1. Field of the Technology
The present disclosure relates to methods and apparatus for controlling discontinuous transmission (DTX) operations in a generic access network (GAN), preferably for mobile communication devices adapted to operate in both wireless local area networks (WLANs) (e.g. IEEE 802.11-based networks) and wireless wide area networks (WWANs) (e.g. public land mobile networks or PLMNs), where communication services of a core network of a PLMN are accessible to the mobile devices via the WLAN in a GAN mode of operation through a GAN controller (GANC).
2. Description of the Related Art
Discontinuous transmission (DTX) for mobile devices operating in wireless wide area networks (WWANs), such as cellular telecommunication networks (e.g. GSM/GPRS based networks), are known. During a voice call, a mobile device maintains a radio link with a base station of a public land mobile network (PLMN) with use of a radio transmitter. During DTX, the radio transmitter is switched off most of the time during speech pauses during the voice call, thereby saving power in the mobile device and reducing the overall interference level over the air interface. A DTX mechanism on the transmit side (e.g. at the mobile device) may have a voice activity detector and a background acoustic noise evaluator. When little or no voice activity is detected on the transmit side, the radio transmitter is switched off after parameters representing background acoustic noise have been sent. On the receive side (e.g. at a base station controller or BSC of the PLMN), the DTX mechanism includes a comfort noise generator which produces “comfort noise” for the listener based on the received parameters. In a Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS) based network, DTX operations are typically performed by the mobile device for uplink communications if commanded so by the network in a System Information Type 3 or Type 6 message. For downlink communications, the mobile device is typically required to handle DTX operations at any time, regardless of whether DTX for uplink communications are commanded so by the network.
Recently, communication services of a PLMN have been made accessible to mobile devices via a GAN (e.g. a WLAN or IEEE 802.11 based network) with use of a GAN controller (GANC) which is connected to a core network of the PLMN. For example, a mobile device may establish a wireless communication link with a wireless access point of any suitable WLAN (in contrast to a base station of the PLMN) available in its coverage area, but utilize voice communication services provided via the core network of the PLMN via the GANC. Thus, radio coverage for obtaining communication services associated with the PLMN may be provided or extended through use of WLANs in locations where PLMN radio coverage would not be economical or technically feasible. Such locations may be large residential areas with a small number of inhabitants. Of course, communication services associated with the PLMN may also be provided via WLANs that are already widely deployed to extend radio coverage.
Current GAN architecture, however, fails to support DTX. When a mobile device operates in the GAN mode of operation via a wireless communication link with a wireless access point of a WLAN, for example, the mobile device has increased power consumption and increases the interference level over the air interface.
Accordingly, what are needed are methods and apparatus for controlling DTX operations in a GAN.